This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Down[unreadable]??s syndrome (DS), a genetic disorder that leads to mental retardation, results from an extra portion of chromosome 21, which includes the A[unreadable]?-amyloid precursor protein gene. By age 40 years and older, people with DS develop neuropathological and neurochemical abnormalities typical of Alzheimer[unreadable]??s disease (AD), including amyloid senile plaques (SPs) and tau neurofibrillary tangles (NFTs).